I am no a biologist, but it seems to me that the most important difference between prokaryotes and eukaryotes is sexual reproduction rather than mitochondria (as I wrote about meanderingly). But neither article can resolve the issue, as my article ignores energy/mitochondria and yours ignores sex.
Still, it feels to me like this article is picking causes and effects kind of arbitrarily: “organism size” and “mitochondria” are taken to be a cause while “genome size” is taken to be an effect, but I don’t see you trying to justify the presence or direction of your arrows of causation.
I read Nick Lane’s The Vital Question and he argues that mitochondria came first and sex second. IIRC, he said that small-genome organisms (bacteria & archaea) do sporadic one-off gene exchange with their neighbors, and that process basically accomplishes the same thing that meiosis accomplishes in eukaryotes, i.e. enabling natural selection to act independently on every gene simultaneously. But sporadic one-off gene exchange is not a mechanism that can scale up to really massive numbers of genes. (I forget why not.) Hence, as genome size started expanding in early eukaryotes, they had to switch to meiosis (with crossing-over) at some point.
I have a vague recollection that he viewed meiosis as easy to evolve, with the justification that meiosis-related machinery can be found in some archaea (or something?). But very low confidence that I’m remembering correctly.
By contrast he definitely goes on and on about how you fundamentally can’t have a large genome without mitochondria [part of his argument is in the OP], and how the process of getting mitochondria (via an archaeon endocytosis-ing a bacterium) was an extremely difficult step evolutionarily.
Not all eukaryotes employ sexual reproduction. Also prokaryotes do have some mechanisms for DNA exchange as well, so copying errors are not their only chance for evolution either.
But I do agree that it’s probably no coincidence that the most complex life forms are sexually reproducing eukaryotes.
I’m pretty sure that I read (in Nick Lane’s The Vital Question) that all eukaryotes employ sexual reproduction at least sometimes. It’s true that they might reproduce asexually for a bunch of generations between sexual reproduction events. (It’s possible that other people disagree with Nick Lane on this, I dunno.)
I see that someone strongly-disagreed with me on this. But are there any eukyrotes that cannot reproduce sexually (and are not very-recently-decended from sexual-reproducers) but still maintain size or complexity levels commonly associated with eukyrotes?
Indeed (as other commenters also pointed out) the ability to sexually reproduce seems to be much more prevalent than I originally thought when writing the above comment. (I thought that eukaryotes only capable of asexual reproduction were relatively common, but it seems that there may only be a very few special cases like that.)
I still disagree with you dismissing the importance of mitochondria though. (I don’t think the OP is saying that mitochondria alone are sufficient for larger genomes, but the argument for why they are at least necessary is convincing to me.)
I am no a biologist, but it seems to me that the most important difference between prokaryotes and eukaryotes is sexual reproduction rather than mitochondria (as I wrote about meanderingly). But neither article can resolve the issue, as my article ignores energy/mitochondria and yours ignores sex.
Still, it feels to me like this article is picking causes and effects kind of arbitrarily: “organism size” and “mitochondria” are taken to be a cause while “genome size” is taken to be an effect, but I don’t see you trying to justify the presence or direction of your arrows of causation.
I read Nick Lane’s The Vital Question and he argues that mitochondria came first and sex second. IIRC, he said that small-genome organisms (bacteria & archaea) do sporadic one-off gene exchange with their neighbors, and that process basically accomplishes the same thing that meiosis accomplishes in eukaryotes, i.e. enabling natural selection to act independently on every gene simultaneously. But sporadic one-off gene exchange is not a mechanism that can scale up to really massive numbers of genes. (I forget why not.) Hence, as genome size started expanding in early eukaryotes, they had to switch to meiosis (with crossing-over) at some point.
I have a vague recollection that he viewed meiosis as easy to evolve, with the justification that meiosis-related machinery can be found in some archaea (or something?). But very low confidence that I’m remembering correctly.
By contrast he definitely goes on and on about how you fundamentally can’t have a large genome without mitochondria [part of his argument is in the OP], and how the process of getting mitochondria (via an archaeon endocytosis-ing a bacterium) was an extremely difficult step evolutionarily.
Not all eukaryotes employ sexual reproduction. Also prokaryotes do have some mechanisms for DNA exchange as well, so copying errors are not their only chance for evolution either.
But I do agree that it’s probably no coincidence that the most complex life forms are sexually reproducing eukaryotes.
I’m pretty sure that I read (in Nick Lane’s The Vital Question) that all eukaryotes employ sexual reproduction at least sometimes. It’s true that they might reproduce asexually for a bunch of generations between sexual reproduction events. (It’s possible that other people disagree with Nick Lane on this, I dunno.)
All Eukaryotes Are Sexual, unless Proven Otherwise says maybe with enough hard work you can find some Malassezia fungi that are asexual, but also the title is pretty clear.
I see that someone strongly-disagreed with me on this. But are there any eukyrotes that cannot reproduce sexually (and are not very-recently-decended from sexual-reproducers) but still maintain size or complexity levels commonly associated with eukyrotes?
Indeed (as other commenters also pointed out) the ability to sexually reproduce seems to be much more prevalent than I originally thought when writing the above comment. (I thought that eukaryotes only capable of asexual reproduction were relatively common, but it seems that there may only be a very few special cases like that.)
I still disagree with you dismissing the importance of mitochondria though. (I don’t think the OP is saying that mitochondria alone are sufficient for larger genomes, but the argument for why they are at least necessary is convincing to me.)